Electrostatic condenser



June 1, 1937.

V J. B. DOW

ELECTROSTATIC CONDENSER Filed June 21; 1952 ETCHZA INVENTOR 93 B. pow

Jennin fi. ATTORNEY Patented June 1, 1937 Jennings B. Dow, United States Navy, Washington, D. 0. Application June 21, 1932, SerialNo. 618,481

2 Claims. (01475-415) (Granted under the act amended April 30,1928; 370 0.

My invention relates broadly to electrostatic condensers and more particularly to temperature operated variable condenser.

One of the objects of' my invention is to pro- 5 vide a variable condenser which will automatically adjust itself to a predetermined capacity in accordance with a given change in temperature.

Another obiectoof my invention is to provide a precision type temperature operated variable con- .10 denser in which the variation in capacity may be made a direct or inverse function of temperaure. A still further object of my invention is to provide a precision type temperature operated is variable condenser in which. the variation in 'capaoity may be made a linear or non-linear function of temperature.

Other and further objects of my invention will be understood from the specification hereinafter following by reference to the accomepanying drawing in which: a l

\ Fig. 1 showsone form of my invention wherein the capacity is made to increase with increasing temperature. Fig. 2 shows a form of the invention wherein the capacity decreases with increasing temperature. Figs. 2A and 2B are sectional views made on lines AA and 3-3, respectively, of Figure 2. Fig. 3 is a side elevational view of one form of adjustable condenser I 30 electrode suitable for use on thermometer tubes of the type shown in Figs. 1 and 2. Fig. 3A is a bottom plan view of the electrode shown in Fig. 3. Fig. 4 shows a still further form of my. invention in which two temperature operated,

5 variable condensers are arranged in tandem.

Figs. 5, 6 and 7 show some of the other forms of condenser electrod'esthat may be substituted for those shown in Figs. 1, 2 and 4. Figs. 5A, 6A

and Marc bottom plan views of the electrodes 40 shown in Figs. 5, 6 and '7, respectively.

Very frequently in the design of scientific apparatus, for example, heterodyne frequency meters and like electrical apparatus, it becomes necessary, in order to guard against the eflects 45 of temperature changes, to place the apparatus in constant temperature ovens, or to make cer-- tain parts of the apparatus of alloys having low temperature coefficients of expansion. Where the apparatus is large and complicated, these I 50 steps are generally inconvenient and frequently result in large manufacturing costs. One alternative method has been to provide an auxiliary compensating capacity across the main capacity and to so design this compensating capacity that 55 it will correct for the effect of changes in the mains substantially constant so long as the top of Mai'ch 3, 1883, as

temperature of the main capacity. Such compensatingv capacities have been based upon the fact that an expanding or contracting metallic element may be made .to displace one or more plates of a variable condenser. These devices 5 have had several deficiencies, namely; the capacity change for a given increase in temperature "is not the exact reverse of that for the equivalent decrease in temperature; .the'sensitivity is not sufllclent to .care for minute changes in temperature, and it is dimeult to design such devices to care for complicated situations wherein the desired change in capacity may be a complicated function of temperature.

The present invention comprises a combina tion of elements to overcome the above deficiencies in temperature operated compensating capacities.

Fig. 1 shows one form of the invention in which reference character i designates a gas type thermometer having a gas chamber 2, a supply of conducting liquid 3 suchas mercury, and a col-. umn 4 of such liquid in a stem 5 of insulating material such as glass. Surrounding a portion of the stem 5 is a lower electrode 6 having av predetermined electrostatic capacity with conducting column B, Surrounding another portion of the stem is an upper electrode 1!. The electrodes 6 and i may be connected to any desired apparatus by connections 8 and 9.

' when the temperature or the medium surrounding gas chamber 2 increases, the liquid col umn 4 is forced upward thus increasing the electrostatic capacity existent between electrodes 6 and T. This capacity is, in effect, the sum of two 35 capacities in series. The first of these capacities is that existent between the lower electrode and the conducting column. In the case of the arrangement shown in Fig. 1, that capacity reof the conducting column remains above the upper part of the lower electrode. The second of these capacities is that existent between the upper electrode and the conducting column. When the temperature decreases, the contraction of the gas in chamber 2 causes the column 4 of conducting liquid to be lowered thus decreasing the capacity in circuitbetween terminals 8 and 9. It will be apparent that in the case of Fig. 1? the lower electrode 6 might have been eliminated by connecting terminal 8 directly with the conducting liquld, however, I prefer that this be not done.

In the case of Fig. 1, it will be noted that the capacity between terminals 8 and 9 increases with increasing temperature. It is generally the case that an inverse characteristic is desired and an arrangement of the invention to provide such a characteristic is shown in Fig. 2 wherein the capacity decreases with increasing temperature. In this case, the excess. liquid is held in a. second chamber II and the column 4 is, supported 'by the pressure 01' the gas in chamber} acting upon the lower part of the liquid column. In all other particulars Fig. 2 is similar to Fig. 1.

In many classes of scientific equipment the capacity compensation which is required, is a complicated function of temperature. To satisfy this need, I have found it useful to make the electrodes 8 and I of special shapes. Electrodes of various shapes are shown in Figs. 3, 5,'6 and 7 where reference characters ii and II, II and'il', l8 and I3, and I4 and Il denote respectively the profile and plan views of four such electrodes. It will be understood that an almost infinite variety of shapes is possible. The) form of electrode shown at H is adjustable by moving the screw elements. I have found it convenient to make the inside diameter of a portion of each 4, each unit is similar to that shown in Fig. 2.

I have found the variable condenser of my invention highly eilicient in its operation and while I have described it in certain preferred embodiments, I desire it to be understood that modifications may be made, and that no limitations are intended other than are imposed by the scope oi the appended claims.

The invention described herein may be manufactured and used by or for the Government oi! the United States for governmental purposes without the payment of any royalty thereon.

What I claim as new and desire to secure by Letters Patent oi the United States is as follows:

1. A variable capacity having in combination a filament of conducting fluid and a metallic element in electrostatic capacity relation with said filament, said metallic element having a support member and screwthread devices for adjusting to a predetermined value the capacity existent between said filament and said screwthread devices.

2. A temperatureoperated variable capacity comprising 'a tube of insulating material. a filament of conducting fluid partly filing said tube,

a metallic member outward of said tube and shaped in such manner that the horizontal distance between. said metallic member and the axis of said filament at one end, varies with the longitudinal displacement oi! said filament along said tube.

' JENNINGS B. DOW. 

